502 U. S. BUREAU OF FISHEEIES 



INTRODUCTION 



During recent years knowledge of the nutritive value of foods has 

 been widely expanded. The great importance of proper diet in pro- 

 moting the right kind of growth and in maintaining life and healtli at 

 their best is now realized. It is generally believed that the food sup- 

 ply as a whole should furnish (a) enough digestible organic foodstuffs 

 to meet the body's needs for energy, (b) enough protein of suitable 

 sorts to supply all needs for essential amino acids, (c) sufRcient min- 

 eral constituents in the right proportions, and (d) enough of the va- 

 rious kinds of vitamins. 



The main bulk of most of the staple foods consists of the following 

 groups of substances: Carbohydrates, fats, proteins, minerals, and 

 vitamins. With the exception of carbohydrates, which are prac- 

 tically lacking, all of these substances are known to be abundantly 

 present in fish and shellfish. 



It was for the purpose of summarizing present knowledge regarding 

 the nutritive value of these substances and the general subject of the 

 composition of fish and shellfish that this document was prepared. 

 The various chapters comprising it were prepared by scientists well 

 qualified to write upon the subject. These papers show that fish and 

 shellfish furnish an excellent supply of very valuable proteins and 

 fats and, as a source of certain vitamins and minerals, they are of 

 great importance. 



Harry R. Beard, 



Chief Technologist. 



I.— CHEMICAL COMPOSITION OF FISH AND SHELLFISH 



By E. D. Clark, Director, and R. W. Clough, Chemist, National Canners Asso- 

 ciation, Northwest Branch, Seattle, Wash. 



HARVESTS FROM THE SEA, LAKES, AND RIVERS 



Not only the land but the sea, lakes, and rivers as well provide 

 mankind with crops of food. In some ways — for example, in the 

 matter of the dependence of animal life upon green plants — land and 

 water are alike. On the other hand, there is a fundamental difference 

 between gathering crops on land and gathering them from the water. 

 Plant and animal products derived from agriculture are produced 

 under the control oi man and are still capable of being increased by 

 the use of more land whenever the demand warrants such a course. 

 Aquatic harvests, however, are neither planted by man nor culti- 

 vated by him, nor does he exercise much, if any, control over them. 



The sea is not merely an expanse of blue water, but may be likened 

 to productive green fields on land — it is alive. The sea, too, has its 

 cycles of life, in which inorganic matter, under the influence of green 

 plants, microscopic or otherwise, is built up into organic matter in the 

 form of vegetable materials. These in turn are eaten by the lower 

 forms of animal life, and then the}^, too, succumb to still higher orders 

 of animal life, until finally man may utilize for his own food some of 

 the links in the chain, such as seaweeds, mollusks, crustaceans, and 

 fishes. Ultimately, however, all animal life in the sea is dependent 

 for its store of energy upon sunlight, which is fixed first by green 

 plants. 



